1. Field of the Invention
The present invention relates to a delay circuit, and more particularly, to a reset circuit with the delay circuit to prevent a system reset due to a noise.
2. Description of Related Art
A liquid crystal display (LCD) includes a display panel and at least a source driver. The source driver outputs display voltages to the display panel in accordance with received video signals. The display panel includes a plurality of pixels for display images, and each one of the pixels has a storage capacitor. The storage capacitors of all pixels are respectively charged in response to the display voltages for displaying colors.
The source driver may malfunction while the operating voltage is not stable yet, for example during turning on or off of the LCD. Therefore a reset circuit is required to ensure the functionality of the source driver.
For another example, the reset operation can be used when turning off the LCD for the storage capacitors of all pixels being discharged to prevent afterimages. The afterimages would influence the visional effect of the LCD, or reduce the reliability of the pixels. The conventional method for eliminating the afterimages is to detect variation of the operating voltage of the LCD. The operating voltage is decreased gradually at power off. When the operating voltage is lower than a threshold voltage, it is determined that the LCD is power off, and then a reset operation is proceeded. For example, by conducting the data lines and scan lines coupled to the pixels, both two terminals of each the storage capacitors are electrically connected to a common voltage so as to have the equivalent potential, and the afterimages are eliminated.
Sometimes a noise would be generated by the power source or other devices of the LCD. In the period of detecting the variation of the operating voltage, the noise would cause the foregoing method a false reset action.